1,4-disubstituted piperazines



Patented Mar. 6, 1951 UNITED; STATES PATENT OFFICE 1,4-DISUBSTITUTED PIPERAZINES Martin Everett Hultquist, Bound Brook, and Kenneth Leon Howard, Westfield, N. J., assignors to American Cyanamid Company, New York, N. Y., a corporation of Maine 'No Drawing. Application November 12, 1947,

Serial No. 785,526

RN H N-Het in which R. is an alkyl, cycloalkyl, aryl, 'or aralkyl radical; Het is the heterocyclic radical, the bond from the l-nitrogen to the heterocyclic radical being to the latter in a position adjacent to a heterocyclic nitrogen; and 1111, m, ya and yr are each hydrogen or lower alkyl radicals.

The group designated by R may be quite widely varied. It may represent variously, an alkyl radical, usually of about one to six carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, amyl, isoamyl, hexyl and the like; a cycloaliphatic radical such as cyclohexyl, ethylcyclohexyl and the like; an aryl radical such as phenyl, tolyl, xylyl, naphthyl or a halogenor hydroXy-substituted derivative thereof; or an aralkyl radical such as benzyl, phenylethyl, methoxy-phenylmethyl or the like.

The group designated as Het is or 6-membered nitrogen-containin heterocyclic radical. It may be substantially any such radical provided the bond thereto is a position adjacent to a heterocyclic nitrogen. Examples include 2- pyridyl, Z-pyrimidyl, 2-pyrazyl, B-pyridazyl, 2-

thiazyl, and their alkyl-- or halogen-substituted heterocyclic ring derivatives.

The compounds of the present invention being lA-substituted piperazines, the latter ring is shown as saturated. However, in addition 'to the 1,4-substituents, the carbon atoms of the ring may also be substituted. As shown in the generic formula above, any or all of 311, ya. ya and 1114 may be either hydrogen or a lower alkyl group, particularly the methyl and ethyl radicals. The invention therefore contemplates 1,4 -disubstituted mono-, di-, triand tetra alkyl piperazines such 'as Z-me'thyl 'or ethyl piperazine, 2,5 and 2,6-dimethyl and diethyl piperazines and tetramethyl piperazine. H The novel [compounds of the present/invention vary in physical character from colorless or light yellow oils, as in those cases where R is a lower alkyl radical, to colorless to yellow crystals where R vis an aryl or aralkyl radical. These compounds are somewhat basic in character. Acid addition salts thereof are in general not too well defined, particularly when R is aryl or aralkyl. Stable, water-soluble salts such as the hydrochloride, hydrobromide, citrate or sulfate may generally be prepared from bases where R is alkyl or cycloalkyl. Some form with water of crystallization, and some areeven hygroscopic;

The bases are only slightly soluble in Water, but

. generally soluble in chloroform, ether, the lower alkanols and, to a varying degree, in naphtha.

Preparation of the compounds is readily accomplished. A general procedure utilizes a suitable l-substituted piperazine, i. e., a methyl, ethyl, phenyl, chlorophenyl, tolyl, phenylethyl, cyclohexyl, or the like piperazine, which is generally available per se or as a salt thereof, such as the hydrochloride. Piperazines with substituents other than nitrogen substitutents, 2-5-dimethyl piperazine for example, may be used.

Either the base or the salt may be used. This is reacted with a halogen-substituted heterocyclic compound having the structure which is to be substituted on the other nitrogen.

The reaction is preferably carried out in the presence of an aqueous alkaline solution. Heat'- a ing and agitation are usually required, ordinarily temperatures from about -200 C. being employed. Heating at these temperatures is maintained for suficient time to insure the reaction being carried as far as possible to completion. About 3 to 20 hours is usually required, although this time may increase or decrease, depending upon the heterocyclic compound being used and depending also upon the batch size and/or the temperature used. An exception occurs in the cases where halogen-substituted pyrimidines are utilized, for chloro or bromopyrimidines generally react exothermically with or without a solvent even under atmospheric conditions when the reaction is once initiated.

Isolation is relatively simple. Where the product forms an insoluble precipitate in the reaction mixture, it may be isolated by filtration and purified by distillation or recrystallization from a suitable solvent, dilute alcohol, or naphtha, for example. When the product is in the form of an oil, it may be extracted with a solvent, such as ether, lsopropyl acetate, or the like. This extract may be dried and the product isolated and purified by distillation or isolated by precipitation from the solvent as its acid addition salt, such as the hydrochloride. The latter salt may be purified by recrystallization from a suitable solvent, such as alcohol, or a solvent mixture, such as acohol-ether, alcohol-isopropyl acetate,

or the like, v

Where it is desirable and possible to form a pure, stable acid salt of these new compounds, this may be accomplished by dissolving the free piperazine product in an essentially anhydrous solvent, adding an essentially anhydrous acid or acid solution to it, and isolating in any of the usual ways the salt thus formed; Acids useful in the preparation of such salts are hydrochlori, sulfuric, citric, hydrobromic and the like. I

Typical compounds in accordance with the present invention include the following:

R-N H N-Het lla 1/4 where w, y2, ya and yi are H, methyl, or ethyl and R and Hot have the following values:

4 EXAMPLE 1 1-phenyZ-4-(2-pyridyl) piperazine A 'sl-ia'pnsion comprising 194 parts l-phenylpiperazine, 92 parts of 2-ch1oropyrazine and 140 parts of a 20 aqueous sodium hydroxide solution is heated, with shaking, for five hours at 200 (3. The crude solid material resulting from the reaction is dissolved in 4000 parts of alcohol, filtered, and the filtrate is treated with an equal R -Ht R Ha tea-03hr 1 These compounds have been found to be pharvolume" of water =-t o :separate a lproduct which is macologically active in various ways. Many of '65 distilled (-B. P. 1 98? 200 C. at 2 mm.) and the them have been found to show anti-spasmodic action, particularly against "neurotropic spasm. More important, a number of the compounds have been found to possess particularly goodamalgesic properties.

The invention will be more "fullyill'ustrated in conjunction with the following examples which are meant to be illustrative only "and not by way of limitation. All parts are by weiglit uiilss otherwise noted.

.yelloW -colored -distillate--is--recrystallized from alcohol as a bright-yellow orystallinaproduct which melts a,t-1-1-9 -120 C.

' EXAMPLEh 1 '5he'1ig l 4 (2epyrimidiilafziiperizzme T0 48.6 parts -o'f1-1'-:phenylpiperazine is added 23 parts- 01 -2 chloropyrimidine. I'he reaction mixture heats spontaneously and ice water:coolmg is Necessary. "-Th'e l'reaution'liproduct :is dissolved in 400 parts of five normal hydrochloric acid, filtered, the filtrate being then treated with 100 parts of 50% aqueous sodium hydroxide whereupon a solid separates. This solid after distillation (B. P. 180-214 C. at 6 mm.) is crystallized from alcohol as a white crystalline material melting at 82-83.2 C.

EXAMPLE 4 1-phenyZ-4- (5-chlloro-2-pyrimidyl) piperazine To 81 parts of l-phenylpiperazine is added 30 parts of 2,5-dichloropyrimidine. The reaction, which begins spontaneously may be moderated by cooling with ice water. The product of the reaction is dissolved in hot dilute hydrochloric acid which contains 50% of ethanol. The product which separates on cooling is the hydrochloride which melts at 245-248 C. The hydrochloride is dissolved in hot dilute aqueous ethanol and is treated with sodium hydroxide whereon the base separates out. The base is recrystallized from hot varnish makers naphtha as a white product which melts at 116.6-117.5 C.

EXAMPLE 5 1 -methyl-4- (Z-pyridyl) piperazine dihydrochloride EXAMPLE 6 1-methyl-4- (z-pyrazyl) piperazine ding/drochloride A suspension of 9.6 parts of chloropyrazine in a so ution previously prepared from 19 parts of l-methylpinerazine d hydrochloride monohydrate in 115 parts of a 30% aqueous sodium hydroxide solution is heated in an autoclave at 200 C. for 16 hours and coo ed. The cooled alkaline solution is extracted with ether. and the ether extract is treated with alcoholic hydrogen chloride. A precipitate of a tan colored dihydrochloride occurs. This salt melts at 243-245 C.

EXAMPLE 7 1-methyl-4- (Z-pyrimz'dyl) piperazine ding/drochloride To a solution of 125 parts of l-methylpiperazine dihydrochloride monohydrate in 690 parts of a 13.8% sodium hydroxide solution is added, at 70 C. over a period of minutes, 5'7 parts of 2-chloropyrim dine. The mixture is heated and stirred at 95-98 C. for one hour and cooled. An oily product forms and is separated from the aqueous layer. This oil is dissolved in absolute ether, and is precipitated by the addition of excess dry hydrogen chloride. The hydrochloride is recrystallized from alcohol. It melts with decomposition over the range 266284 C.

EXAMPLE 8 1-methyl-4- (z-t iazyl) piperazine dihydrochloride 40 parts of z-chlorothiazole is suspended in a solution of parts of l-methylpiperazine dihydrochloride monohydrate in 300 parts of a 22% aqueous sodium hydroxide. This mixture is heated for five hours at 150 C. in an autoclave. The product is filtered and the aqueous layer is extracted with ether. Ether is removed from the extract and the residue is distilled. The fraction boiling at -141 C. at 3 mm. pressure is collected, dissolved in ethanol, treated with hydro gen chloride and the resultant salt is collected.-

hydrochloride softens at about 242 C. and melts at 245247 C.

We claim:

1. 1,4-disubstituted piperazine of the type and acid salts thereof in which 111 or 112 are selected from the group consisting of hydrogen. methyl and ethyl, R is a radical selected from the group consisting of the alkyl and hydroxyalkyl radicals of 1-6 carbon atoms, the cyclohexyl, phenyl, tolyl, naphthyl and benzyl radica s and the halogen substituted phenyl and tolyl radicals, and-Het is selected from the group consisting of the five and six membered nitrogen-containing heterocyclic radicals in which nitrogen is the only hetero atom and thiazyl, the bond from the piperazine being to a formula position in the heterocyclic ring.

2. A substituted piperazine according to claim 1 in which Het is 3. A substituted piperazine according to claim 1 in which -Het is if N L 4. A substituted piperazine according to claim 1 in which --Het is 5. A substituted piperazine according to claim 1 in which -Het is MARTIN EVERETT HULTQUIST. KENNETH LEON HOWARD.

No references cited. 

1. 1,4-DISUBSTITUTED PIPERAZINE OF THE TYPE FORMULA 